Assessment Comments
Assessment is based on: (1) results of IDNR/SHL biological monitoring near Teeds Grove in 1999 & 2007 and (2) results of routine water quality monitoring conducted at station ER02.4 from 2002 through 2004 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA.
Basis for Assessment
Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, and due to the completion of a Use Attainability Analysis, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: The Class A1 (primary contact recreation) uses are “not assessed” due to the lack of information upon which to base an assessment. The Class B(WW) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of biological monitoring in 1999 & 2007. Results of routine water quality monitoring conducted from 2002-2004 as part of LTRMP monitoring, however, do not suggest problems with chemical / physical water quality. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach. The sources of data for this assessment include (1) results of IDNR/UHL biological monitoring near Teeds Grove in 1999 & 2007 and (2) results of routine water quality monitoring conducted at station ER02.4 from 2002 through 2004 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA.
EXPLANATION: The Class A1 uses are “not assessed” due to the lack of water quality information upon which to base an assessment. LTRMP monitoring does not include sampling for indicator bacteria.
This monitored/evaluated aquatic life assessment was based on data collected in 1999 and 2007 as part of the IDNR/SHL stream biomonitoring project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 FIBI score was 17 (poor) and the BMIBI score was 41 (fair). The 2007 FIBI score was 42 (fair) and the BMIBI score was 48 (fair). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 1/2 times and passed the BMIBI BIC 0/2 times in the last 10 years. The biological impairment criteria were determined from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2004.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year peiod to be considered “monitored”. This segment had multiple samples collected in the previous 10 years; however, the samples were not collected during a five-year period. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s Section 303(d) list of impaired waters.
In addition to biological monitoring, this assessment is based on chemical/physical water quality data for 45 samples collected from Elk River at station ER02.4M during the period January 2002 through September 2004 as part of the Long-Term Resource Monitoring Program. Samples were collected approximately every two weeks; samples were collected during all months of the year. The parameters analyzed included dissolved oxygen, pH, ammonia-nitrogen, total phosphorus, total nitrogen, total suspended solids, and chlorophyll. A summary of these data show no violations of the Class B(WW) water quality criteria for temperature, pH, dissolved oxygen, or ammonia-nitrogen in the 45 samples collected. LTRMP monitoring was not conducted at this station during the period 2005 through 2006.
Despite the results of chemical monitoring that suggest moderately good water quality in Elk River (at least in terms of compliance with Iowa Water Quality Standards), the results of biological monitoring suggest an impairment ("partial support") of the aquatic life uses. Because stream biota (fish and aquatic macroinvertebrates) integrate water quality impacts over the long-term, the results of biological monitoring are typically weighted more than results of chemical monitoring when determining support of aquatic life uses for purposes of Section 305(b) reporting. This approach is consistent with recommendations in U.S. EPA's guidelines for Section 305(b) reporting (see U.S. EPA 1997b, page 3-21). Thus, considering the "full support" suggested by results of chemical monitoring, and the "partial support" suggested by results of biological monitoring, the aquatic life use of this segment of Elk River are assessed as "partially supported" for the 2012 assessment/listing cycle. This assessment is consistent with results of previous biological monitoring that has suggested impairments to the aquatic life uses of this river segment.
Fish consumption uses remain "not assessed" due to the lack of monitoring in this stream reach.
